1. Field of the Invention
The present invention relates to a method of extracting a call set-up failure probability and a premature disconnect probability, which are quality factors necessary for the quality control of a data communication network, by using network data. In particular, the present invention relates to a method of extracting a call set-up failure probability and a premature disconnect probability by using network data which extracts the call set-up failure probability and the premature disconnect probability by using various call information which are included in communication network data.
2. Description of the Related Art
With the proliferation of information communication services throughout the world, various data communication networks are being constructed and used. However, the problems encountered with these data communication networks are that even though users need high speed/high quality information communication services such as multimedia services, the environment for service provision including data communication networks fails to meet users' needs.
Therefore, the ITU-T has defined quality factors and quality values of data communication in order to provide better services of high quality in providing information communication services by using a data communication network, and has recommended it to be used by communication network operating bodies. Currently, some of the quality factors recommended by the ITU-T are used by almost all communication network operating bodies as their quality standard for a data communication network to control the quality of data communication.
Quality values recommended and used by the ITU-T and communication network operating bodies include the following: a call set-up delay, a call set-up error probability, a call set-up failure probability, a data packet transfer delay, a throughput capacity, a residual error probability, a premature disconnect probability, a premature disconnect stimulus probability, a reset probability, a reset stimulus probability, a clear indication delay, a call clear failure probability, a service availability, and a meantime between service outage.
A method of extracting the call set-up failure probability and the premature disconnect probability was presented by the ITU-T based on the system as shown in FIG. 1. The call set-up failure probability is a measure representing the quality of call set-up, and can be expressed by a rate of the number of call failures to the number of total call attempts. The premature disconnect probability is a measure representing the reliability of user information transmission, and can be expressed by the probability that a virtual call will experience a premature disconnect event for arbitrary intervals due to some causes arising from within the path constituted by the virtual call.
The system in FIG. 1 comprises a measurement control unit 1, a unit subjected to measurement 2, and a measuring device 3 which can monitor a protocol between the measurement control unit 1 and the unit subjected to measurement 2. In accordance with this system environment, a line, which can represent a data communication network, is selected. The measurement control unit 1, the unit subjected to measurement 2, and the measuring device 3 are installed at the center, on the line subjected to measurement, and on the network line, respectively. Then, a call set-up test and a premature disconnect test are performed. In this case, the restrictions at the time of extracting quality values are applied by excluding some conditions such as unavailable conditions.
However, the present packet-switched public data network (PSPDN) is spread over wide areas, and the number of lines is spread over several ten thousands. Therefore, the quality value calculated based on a selected portion of the total lines of the packet-switched public data network may not represent the quality of the whole packet-switched public data network. In the past, a data communication network supported a low speed model protocol, however, various speeds and protocols are currently supported by the communication network. For this reason, the measurement control unit 1, the unit subjected to measurement 2, and the measuring device 3 which can monitor a protocol between the measurement control unit 1 and the unit subjected to measurement 2 are needed to implement a system which can extract quality values of a communication network with the various speeds and protocols reflected. Also, there were many difficulties in implementing the system because it took a long period to extract quality values. For example, at least 200 call set-up tests, and call maintenance tests over 55 hours must be performed to calculate the quality standard value (type A for the domestic purpose) which is 5.times.10.sup.-3 for a call set-up failure probability, and 5.times.10.sup.-6 for a premature disconnect probability. This method estimates the quality value of the whole packet-switched public data network by using a few sample lines. Therefore, it is difficult to locate local lines whose quality have been degraded, to separate them from the network, and to analyze the cause of the degradation for improving the quality of a communication network. It is also difficult to reflect quality values into the design and engineering of the packet-switched public data network. Further, it is very costly to implement such a system.
Therefore, there have been problems in the art that the method of extracting quality values in accordance with the ITU-T is not adequate in view of the representativeness of quality values, the costs of implementing the system, and the efficiency of quality control; therefore the method is not adequate for use by communication network operating bodies.